function Jq(ele) {
    // 1 用qsa
    // 2 保存起来
    let eles = document.querySelectorAll(ele) 
     // [li标签对象, ..., li标签对象]
    for (let i=0; i<eles.length; i++)
    {
        // this.i = eles[i]
        this[i] = eles[i]
    }
    this.length = eles.length
}
Jq.prototype.css = function(cssName, cssValue) {
 // this === 实例化对象 === 构造函数中this
    for (let i=0; i<this.length; i++)
    {
        this[i].style[cssName] = cssValue
    }
}

function $(ele) {
    return new Jq(ele)
}